Dynamic location management and activity-based mobility modelling for cellular networks

Abstract

The challenge of supporting rapidly growing numbers of mobile subscribers, while constrained by limited radio spectrum, is being faced by cellular network operators worldwide. The standard technique for cellular networks is to decrease radio cell size, thereby maintaining a supportable subscriber density. However, smaller cell sizes result in increased signalling for location management procedures, which reduces the bandwidth available for user traffic.

Location management is an essential function in cellular networks that allows the network to maintain the position of subscribers, in terms of location areas. Location areas in current systems, such as GSM, consist of static and arbitrarily-defined collections of cells, which do not take into account individual subscriber mobility patterns, either in space or time. Consequently, performance suffers significantly in terms of signalling requirements.

A location management algorithm is proposed which uses the mobility history of individual subscribers to dynamically create individualized location areas, based on previous movements from cell to cell. The average visit duration in each cell is also maintained and is used to define paging areas, or subsets of the location area which are most likely to contain the subscriber.

To test the proposed algorithm, a stochastic mobility model was developed based on daily sequences of activities and their associated durations and locations. The mobility model outputs the cells traversed by a subscriber over time. A call arrival distribution, together with the mobility model, provided a simulation framework used to compare the proposed algorithm with variations of the static location management scheme.

Overall, the dynamic algorithm generated significantly lower location management costs, in terms of signalling messages generated, for all parameters examined. The proposed dynamic algorithm requires slightly increased memory and processing capabilities in the mobile station and network, but can significantly reduce location management signalling compared to current techniques.